Android : No App Icon on ActionBar

There are a lot of queries here about adding icons to ActionBar but none solved my problem. If you know a duplicate of this question, feel free to comment or close this question.

I migrated my project to IntelliJ and I didn't encounter this problem with my previous IDE (Eclipse).

PROBLEM: The app icon is not displayed in the ActionBar.

I think it's supposed to be added by default that's why I can't add it through its XML

Here's its XML

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".MainActivity" >

    <item android:id="@+id/action_settings"
        android:title="@string/action_settings"
        android:orderInCategory="100"
        app:showAsAction="always" />
</menu>

Thanks!